In encapsulating a component in a matrix, the matrix material is generally heated to a sufficiently high temperature to provide a plasticized mass which facilitates embedding or coating of the component. Upon cooling, the matrix material hardens or becomes solidified and protects the encapsulant from undesirable or premature reaction. Grinding of a solidified or glassy product to obtain a desired particle size for incorporation in foods or beverages generally results in the formation of irregularly-shaped pieces and rough surfaces. Irregularly shaped pieces and creviced surfaces tend to result in non-uniform encapsulant release, increased diffusion of liquid encapsulants, and increased penetration of oxygen and water which may deleteriously affect sensitive encapsulants, such as readily oxidizable components. Incorporation of a water soluble antioxidant, such as an acidic antioxidant into a dry matrix material may not be effective for preventing oxidation because of the substantial absence of a fluid reaction medium for the antioxidant or immobilization of the antioxidant. Increasing the water content of the matrix material to improve antioxidant mobilization may result in a water activity which is not shelf stable, may adversely affect a desirable crispy texture, or may adversely affect the release properties of the matrix.
Prophylactic and therapeutic benefits of omega-3 fatty acids and their role as anti-inflammatory agents are well-proven. Recent clinical studies have further suggested that consumption of sufficient amounts of these polyunsaturated fatty acids may be adequate for intervention treatment for animals and humans suffering from rheumatoid arthritis. Dietary sources of omega-3 fatty acids can be found mainly in foods from marine sources such as algae and fish. In most populations, however, the nutritional benefits of polyunsaturated fatty acid (PUFA) compounds cannot be realized due to the low consumption of fish and edible algae. With the U.S. Food and Drug Administration's current allowance for health claims relating to intake of omega-3 fatty acids for protection from heart disease, there is an increased interest in fortifying food products with these components. One main problem that hinders the incorporation of omega-3 PUFA oils into processed foods is the oil's high degree of unsaturation, its susceptibility to oxidation and the subsequent deteriorative effects on flavor and aroma of the oil.
The stabilization of omega-3 fatty acid compounds is disclosed in U.S. Pat. No. 5,567,730 to Miyashita et al. One or more of the compounds or an oil or fat containing the compounds is dispersed in an aqueous solution optionally using a surface active agent or an emulsifying agent, such as Tween 20, a sucrose fatty ester, a sorbitan fatty ester, lecithin and a monoglyceride. A water soluble or oil soluble anti-oxidizing agent or a clathrate inclusion compound such as cyclodextrin can be used together with the surface active agent or emulsifying agent. When no surface active agent or emulsifying agent is used, the amount of the omega-3 fatty acid to added to the aqueous system to allow the stabilization is 0.0001-0.3 (w/v)%. When the agent is employed the amount of the omega-3 fatty acid to be added to the aqueous system to allow the stabilization is still only 0.0001-7 (w/v)%. Production of shelf-stable, discrete, solid particles which contain omega-3 fatty acids or fish oils is not disclosed.
International patent publication no. WO 95/26752 (published Oct. 12, 1995) discloses the production of a food product for the enteric supply of a fatty acid, a fatty acid containing substance, an amino acid, or an amino acid containing substance by at least partially complexing the fatty acid or amino acid in the amylose helix of starch to mask the acid. The product may contain one or more flavors and colors, fat soluble substances, anti-oxidants, or pharmacologically effective substances. The components may be first dry mixed and subsequently fed into an extruder where they are substantially mixed and subsequently heated above the gelatinization temperature of the starch to obtain an elasticized mass which is extruded and formed into pellets. However, heat-sensitive components would be destroyed during the heating step.
U.S. Pat. No. 4,895,725 to Kantor et al discloses the microencapsulation of oil-based bioactive materials, such as fish oil which contain polyunsaturated fatty acids. The microcapsules are prepared from an emulsion of fish oil and an enteric coating suspended in a basic solution, preferably a 25% suspension of ethyl cellulose in ammonium hydroxide. The emulsion is atomized into an acidic solution using an inert gas such as nitrogen or argon. The resulting microcapsules are filtered out of the acidic solution, washed with water and a surfactant and dried. The conditions under which the emulsion is atomized determines the particle size, which can range from about 0.1 to 500 microns, preferably between about 0.5 to 100 microns. However, the enteric coating, such as ethylcellulose is not solubilized and the resulting suspension requires atomization into an acidic aqueous solution to produce microcapsules. Filtering and several washing steps are needed to recover the microcapsules. Control of oil droplet sizes by homogenization so as to avoid coalescence and obtain a substantially uniform oil droplet size is not disclosed. Protection or prevention of the microcapsules from cracking, or rupturing is not taught. Also, prevention or inhibition of diffusion of the oil through the capsule wall to the microcapsule surface, and penetration of oxygen through the capsule wall into the oil are not disclosed.
The production of expanded products is disclosed in European patent publication nos. EP 0465364 A1 (published Jan. 8, 1992) and EP 0462012 A2 (published Dec. 18, 1991), U.S. Pat. No. 3,962,416 to Katzen and U.S. Pat. No. 3,786,123 to Katzen. The two European patent publications disclose the production of an anti-obesity food and a method for making it by extrusion of starches with fatty acids into an expanded product having densities between 0.1 and 0.3 g/cm3. U.S. Pat. No. 3,962,416 to Katzen discloses an expanded product which contains at least one nutrient and one gelatinized starch.
U.S. Pat. No. 3,786,123 to Katzen discloses a method for producing encapsulated nutrients using extrusion temperatures of between 250° F. and 400° F. and extrusion pressures of between 200 psi to 2500 psi. A high protein encapsulating agent containing up to 40% starch may be used. The starch is gelatinized and extruded into an expanded product.
However, in producing a product having controlled release or delayed release, excessive expansion or puffing may result in too rapid release properties or may undesirably expose an encapsulant to destructive reactions. For example, in the case of an edible composition for delivering encapsulated pharmaceutically or nutritionally active components or a non-edible agricultural product for delivering biocides or herbicides, it is desirable that the products have a substantially spherical shape and a high density. Such products exhibit a substantially low ratio between surface area and volume and thus minimize or prevent surface related destructive reactions that occur upon exposure to air or oxygen and light. The spherical shapes and high densities also minimize the surface which would be available to expose embedded material which is not encapsulated. Furthermore, for edible products for delivering pharmaceutically or nutritionally active components, it is desirable that the products are capable of being consumed or swallowed without chewing or substantially no chewing. Avoiding the need for mastication, further assures that the products reach the digestive tract without substantial enzymatic hydrolysis in the mouth. Furthermore, it helps to control or reduce dissolution of the product in gastric juice and to control the release of the embedded or encapsulated components in the stomach and/or in the intestine.
International patent publication no. WO 92/00130 (published Jan. 9, 1992) discloses a continuous process for obtaining an encapsulated, biologically active product in a starchy matrix. A biologically active agent and starch are mixed before extrusion and extruded as a blend, with the encapsulant or biologically active agent being heated together with the starch. Alternatively, a core material to be encapsulated may be added and blended with an aqueous dispersion of starch after the starch and water have been subjected to an elevated temperature sufficient to gelatinize the starch. The extrusion process, it is disclosed, exposes the mix to high shear mechanical action at a temperature above the gelatinization temperature of the starch. The use of extrusion barrel temperatures of between about 58° C. and 98° C. are disclosed. While these barrel temperatures may be above the gelatinization temperature of starch, the extruder utilized has barrel sections that are only three l/d long. The screw speeds utilized, between 400 rpm and 200 rpm, result in a very short residence time of the blend inside the extruder and barely allow heating up of the starch water mix. As a result, the temperatures obtained are generally too low to obtain substantial gelatinization of native starches. Additionally, the barrel temperatures used are particularly too low for substantial gelatinization of high amylose starch which generally gelatinizes at temperatures substantially above 100° C., for example at 125° C. The use of extrusion barrel temperatures which are not sufficiently high to substantially or completely gelatinize the starch may not form a sufficiently continuous, plasticized and homogeneous matrix for effective embedding or encapsulation.
In addition, the use of relatively low extrusion temperatures, high speed mixing, and a high viscosity starch composition generally requires a high mechanical energy input. High shear is directly related to high specific mechanical energy, which in turn increases the molecular destructurization and dextrinization of starch. Breakdown of the starch molecules, and in particular the amylopectin, increases the solubility of the extruded starch composition in aqueous systems as described in P. Colonna, et al., “Extrusion Cooking of Starch & Starchy Products,” Extrusion Cooking, C. Mercier, et al. pp. 247-319, AACC, St. Paul, Minn. (1989) and F. Meuser, et al, “A Systems Analytical Approach To Extrusion,” Food Extrusion Science & Technology, ed. J. Kokini, Dekker Publ., pp. 619-630 (1992). Increased solubility of the extruded starch in aqueous systems decreases the stability of the product against moisture and subsequently diminishes or shortens the protection and controlled release of the embedded or encapsulated substances. In addition, subjecting the encapsulant to the same high shear and high temperature conditions to which the starch is subjected may adversely affect the encapsulant by at least partially destroying it or decomposing it into unknown solid or volatile substances.
Pregelatinized starch is used in numerous applications in the food industry as a swelling agent and for accelerated and extended water absorption in foods such as soups, sauces, instant puddings, baby food, and thickening agents. However, it has been found that the use of pregelatinized starch or the use of starch as the only matrix material during extrusion cooking generally results in a matrix which releases the encapsulant too quickly. It has been found that the penetration of water into a pure starch matrix causes early release of the encapsulant into the environment. Generally the time to release 100% of the encapsulant is too short to provide a desirable time-release or controlled-release which is effective for delivering the encapsulant at a desired location or time.
U.S. Pat. No. 5,183,690 to Carr, et al. discloses a continuous process for imparting predetermined release properties to an encapsulated biologically active agent in a matrix of starchy material. The starchy material, an active agent, and water are continuously blended in an ingredient stream wherein the starchy material is at a solids concentration of at least 40%. The ingredients stream is continuously extruded as an extrudate and the extrudate is continuously recovered. The conditions of blending, extruding, and recovering are preselected to yield the predetermined release properties. The temperature is elevated to at least about 65° C. to effect gelatinization of starch and assure an essentially molecular dispersion of the starch in the water. Alternatively, the core material to be encapsulated is added and blended with the aqueous dispersion of starch after the starch and water has been subjected to an elevated temperature sufficient to gelatinize the starch. In this embodiment the aqueous starch stream containing gelatinized starch may be lowered to a temperature as low as about 25° C. before the core material to be encapsulated is added and subjected to high-shear mechanical action. Under such low temperature conditions of admixture it is disclosed, the activity of sensitive biological material, such as bacteria and viruses, is preserved and loss of volatile organic materials is minimized. The rate of swelling of the products in water and the rate of release of active agents are controlled by altering the amount of water present in the starch-agent-water blend during processing. As the amount of water is decreased, both the swelling rate and the release rate increase. The rate of swelling of the products in water and the rate of release of active agent are also controlled by passage of the extrudate containing starch-agent-water through an exit die of various dimensions. As the exit die is reduced in size, both the rate and extent of swelling increase and the rate of release of agent increases.
U.S. Pat. No. 6,190,591 and International Publication No. WO 98/18610, published on May 7, 1998, both to Bernhard H. van Lengerich, the disclosures of which are herein incorporated by reference in their entireties, disclose a controlled release particulate composition which contains a hydrophobic component for controlling the release of an encapsulated and/or embedded active component from a plasticized matrix. High water binding capacity agents may also be used to delay or control the release of the encapsulant from the matrix. A high amount of plasticizer is employed to facilitate plasticization of the matrix material at low shear and is then reduced prior to adding the encapsulant to facilitate subsequent forming and to reduce post extrusion drying. Liquid active components or solutions, dispersions, emulsions or suspensions may be injected into the plasticized matrix material. The controlled release or delayed release composition may be produced without substantial expansion of the matrix material to thereby avoid production of a low density product which prematurely or too rapidly releases the encapsulant or the embedded component.
Copending U.S. application Ser. No. 09/233,443, filed Jan. 20, 1999 in the name of Bernhard H. Van Lengerich, International Publication No. WO 00/21504 published on Apr. 20, 2000, U.S. Pat. No. 6,500,463 to Van Lengerich, and International Publication No. WO 01/25414 published on Apr. 12, 2001, the disclosures of which are herein incorporated by reference in their entireties, disclose a continuous process for producing shelf-stable, controlled release, discrete, solid particles from a liquid encapsulant component which contains a sensitive encapsulant, such as a heat sensitive or readily oxidizable pharmaceutically, biologically, or nutritionally active component, such as essential and/or highly unsaturated fatty acids. A liquid encapsulant component which contains an active, sensitive encapsulant, such as a live microorganism or an enzyme dissolved or dispersed in a liquid plasticizer is admixed with a plasticizable matrix material. The matrix material is plasticizable by the liquid plasticizer and the encapsulation of the active encapsulant is accomplished at a low temperature and under low shear conditions. The active component is encapsulated and/or embedded in the plasticizable matrix component or material in a continuous process to produce discrete, solid particles. The encapsulants may be suspensions of microorganisms in water, and suspensions or dispersions or emulsions or solutions of vitamins, enzymes, minerals or trace elements in water or other liquids. The liquid content of the liquid encapsulant component provides substantially all or completely all of the liquid plasticizer needed to plasticize the matrix component to obtain a formable, extrudable, cuttable, mixture or dough. Removal of liquid plasticizer prior to extrusion is not needed to adjust the viscosity of the mixture for formability.
U.S. Pat. No. 5,064,669 to Tan et al relates to the production of controlled release flavors for microwaveable foods. Controlled-release, flowable flavoring powders are produced by: a) heating a high-melting-point encapsulating or enrobing material (fat and/or wax and one or more emulsifiers) to melt the starting material; b) mixing one or more water-containing flavor compositions with a texture conditioning agent; c) mixing the flavor compositions and texture containing agent with the molten fat or wax to obtain a homogeneous mixture in the form of an emulsion; and d) chilling the flavor composition-containing mixture to provide discrete particles of solid encapsulated flavoring agent.
U.S. Pat. No. 5,106,639 to Lee et al discloses a process for preparing fatty fodder additives by mixing an emulsifier, a carrier, and a fat material containing omega-3 fatty acids to produce an emulsion, homogenizing the emulsion, and drying the emulsion to produce a powdered fat. The emulsion may also contain water and whey. The carrier may be soybean protein, skim milk solids, starch, pectin, gelatin, casein, collagen, and egg protein. After spray drying or fluidized bed drying, the particulate fat product generally has a particle size ranging from about 0.1 to about 1.0 millimeters. An enteric coating comprising a cellulosic material may be applied to the powdered fat.
U.S. Patent Application Publication No. US 2004/0017017 A1, published Jan. 29, 2004 to Van Lengerich et al, the disclosure of which is herein incorporated by reference in its entirety, discloses production of a stabilized oil-in-water emulsion which contains a readily oxidizable component or a heat sensitive component. An antioxidant for prevention of oxidation of the active, sensitive encapsulant, and a film-softening component or plasticizer for the film-forming component may be included in the emulsion. The emulsion is stabilized by subjecting it to homogenization. Shelf stable, controlled release, discrete, solid particles or pellets which contain an encapsulated and/or embedded readily oxidizable component or a heat sensitive component are produced by first reducing the water content of the stabilized emulsion. Reduction of the water content causes the film-forming component to form a film around the oil droplets and encapsulate the encapsulant. The water content of the homogenized emulsion may be reduced by spray-drying to produce a powder. In other embodiments, after homogenization, the water content of the emulsion may be reduced by admixing the emulsion with at least one matrix material to thereby encapsulate the film-coated oil droplets within the matrix material. After the water content of the emulsion is reduced, a protective coating is applied on the film-coated oil droplets to obtain pellets. The protective coating helps to prevent diffusion of the oil component to the surface of the pellets, and helps to inhibit penetration of atmospheric oxygen into the encapsulated oil component. The protective coating also fills in or seals any crevices, cracks, irregularities, or pores in the underlying substrate and helps to provide a more smooth surfaced, uniform pellet or cluster. After application of the protective coating, the pellets may be dried to obtain the final encapsulated product.
Inclusion of an antioxidant in the oil phase or oil droplets generally makes it mobile for interacting with any ambient oxygen invading the encapsulated readily oxidizable component. However, addition of an antioxidant to the emulsion may result in an increase in emulsion viscosity due to interaction with certain proteins and could impede the attainment of small oil droplet sizes. Also, it would also be beneficial to include an antioxidant in the matrix material so as to help prevent the oxygen from even reaching the readily oxidizable component in the oil droplets. However, when incorporating an acidic antioxidant into the matrix material, it has been found that upon drying the pellets to a shelf stable water activity, the acidic antioxidant tends to crystallize and become immobilized. Immobilization of the acidic antioxidant inhibits its interaction with invading ambient oxygen.
The present invention provides a process for producing discrete, particulate, shelf-stable encapsulated sensitive components, such as heat-sensitive components or readily oxidizable components, such as omega-3 fatty acids. Exposure of the sensitive components to atmospheric oxygen may be substantially prevented without the need for a protective surface coating on the particulates. The process avoids the need to incorporate substantial amounts of antioxidants in the oil component which tend to react with certain proteinaceous film-forming components or which tend to increase viscosity of the emulsion which may impede homogenization and result in reduced encapsulation efficiency. In accordance with the present invention, an acidic antioxidant may be incorporated in a matrix material without loss of mobility for interaction with any invading ambient oxygen. The processes of the present invention may be used for the continuous production of an edible composition for delivering pharmaceutically or nutritionally active components, such as omega-3 fatty acids. The particulates containing encapsulated fish oils, and food products containing the particulates do not exhibit rancid odors or tastes for extended periods of time, for example for at least about six months.